DESCRIPTION (Applicant's Abstract): Evidence exists that multiple subtypes of neuronal nAChRs are present throughout the nervous system, with differing pharmacology and regulation. Chromaffin cells from the adrenal medulla express neuronal nAChRs. Although these nAChRs are the principal receptors mediating release of catecholamines from the adrenal gland, little information is available on the molecular composition and regulation of these physiologically important receptors. These proposed studies address the hypotheses that heterogeneous populations of nAChRs are expressed in adrenal chromaffin cells and that the cytoskeletal network plays an important role in regulating nAChR activity. In these studies nAChR subtypes mediating secretion will be characterized. Alterations in subunit composition will be directly correlated with changes in agonist/antagonist sensitivity and secretion. The specific aims of the proposed research are 1) to identify the nAChR genes expressed in adrenal chromaffin cells and isolate full-length cDNAs for the expressed genes, 2) to determine which nAChRs subtypes are expressed and 3) to determine the functional contribution of the various nAChR subunits/subtypes and investigate their regulation. Northern analysis, PCR techniques and cDNA cloning will be used to determine which nAChR genes are expressed. Binding experiments, immunopurification and affinity chromatography will be used to characterize nAChR subtypes, and antisense oligonucleotides and specific nAChR antibodies will be used to probe the functional role of specific adrenal nAChR subunit gene products and specific nAChR subtypes in adrenal secretion. These studies should contribute significantly to our current knowledge of adrenal nAChRs and may also contribute to our basic understanding of neuronal nAChRs and their regulation.